Surface Brillouin scattering in photonic crystal fibers

We report, to the best of our knowledge, the first experimental observation of surface Brillouin scattering in silica-based photonic crystal fibers, arising from the interaction between guided light and surface acoustic waves. This was achieved using small-core and high air-filling fraction microstructured fibers that enable a strong opto-acoustic coupling near the air holes while mitigating the acoustic leakages in the microstructured cladding. It is further shown that this new type of light scattering is highly sensitive to the fiber air-hole microstructure, thus providing a passive and efficient way to control it. Our observations are confirmed through numerical simulations of the elastodynamics equation.